1. Technical Field
The present invention is generally related to multimedia delivery over the Internet. Particularly, the present invention is related to techniques providing media services including movies with multiple audio streams on an open network, such as the Internet.
2. Description of the Related Art
Continuous or on-demand media data such as video and audio programs have been broadcasted over data networks (e.g., the Internet). Broadcast of such media information over data networks by digital broadcasting systems provides many advantages and benefits that cannot be matched by current television cable systems or over-the-air broadcasting.
With the media-over-network systems, service providers are often able to draw viewers into an exciting, interactive and enhanced television or viewing experience. Video-On-Demand (VOD) or Near Video-On-Demand (NVOD) collectively referred to herein as VOD programs are examples of the interactive television programs typically provided by a service provider to its subscribers. VOD programs are video sessions that subscribers can order whenever they want or per NVOD schedules. FIG. 1 shows a video delivery system 100 that is commonly used for delivering VOD programs over a network. The video delivery system 100 includes a video server 102 that is sometimes referred to as a head-end. Through a data network 104, the video server 102 can provide continuous, scheduled and video-on-demand (VOD) services to respective client machines 106-1, 106-2, . . . 106-n (i.e., its subscribers). The server 102 is further coupled to a media storage device 112 that may be configured to store various media files (e.g., movies or news footage). The media storage device 112 must be on-line, store and supply titles scheduled or demanded for delivery to any of the client machines 106-1, 106-2, . . . 106-n. 
To ensure quality of service (QoS), the bandwidth requirement of the network path (e.g., 108-1, 108-2, . . . 108-n) to each of the client machines 106-1, 106-2, . . . 106-n has to be sufficient. However, as the number of the subscribers continues to increase, the demand on the bandwidth of the backbone network path 110 increases linearly, and the overall cost of the system 100 increases considerably at the same time. If the server has a fixed bandwidth limit and system support capability, an increase in the number of subscribers beyond a certain threshold will result in slower transfer of data to clients. In other words, the transmission of the video data over the network 104 to the subscribers via the client machines 106-1, 106-2, . . . 106-n is no longer guaranteed. When the video data is not received in a client machine on time, the display of the video data may fail or at least become jittery.
To alleviate such loading problem to the video server 102, a video delivery system often employs multiple video servers as rendering farms, perhaps in multiple locations. Each of the video servers, similar to the video server 102, is configured to support a limited number of subscribers. Whenever the number of subscribers goes beyond the capacity of a video server or the bandwidth thereof, an additional video server needs to be deployed or additional bandwidth needs to be allocated. Subsequently, overall costs go up considerably when more subscribers sign up with the video delivery system 100.
Although more servers may be added to accommodate more subscribers, the implementation of the video server 102 present many challenges to consider in delivering programs over an open network. In general, movies come with a number of different audio tracks. Typically, a movie may include respective audio tracks in English, Spanish, French, Chinese, or other languages. Streaming multiple audio streams for each video increases the bandwidth requirements of the network. Increasing the bandwidth requirement for multiple audio tracks makes the overall cost of the system 100 too costly and may not be practically possible.
There have been various effort towards providing multiple audio tracks for a movie. One approach is to treat video with different audio tracks as different movies. For example, a video with English audio track is treated as a different movie from the same video with Spanish audio track. However, such an approach wastes storage space and bandwidth by duplicating videos for different audio tracks.
Thus, there is a need for improved techniques for cost effective ways for service providers to deliver programs with multiple audios to subscribers over an open network.